Heavy alcohol consumption is strongly linked to an increased incidence of hypertension and its associated complications, such as stroke. The mechanism for this effect of ethanol is unknown. Ethanol has been shown to contract blood vessels directly and to alter the response produced by other vasoconstrictors. Tolerance develops to these actions of ethanol. Recently, it has been demonstrated that the endothelial cells lining blood vessels are obligatory in the action of many important hypotensive agents. The role played by endothelial cells in the action of ethanol had not been investigated unitl recently by this laboratory. The purpose of this proposal is to continue our investigation of the role played by endothelial cells in the vascular effects of ethanol. In particular, it has recently been demonstrated that the endothelial cells play an obligatory role in the expression of tolerance to the direct vasoconstrictor effect of ethanol. It has been hypothesized that an endothelium-dependent relaxing factor (EDRF) is responsible. The proposed experiments will investigate this hypothesis further. Initially, it is proposed that ethanol induced changes in cyclic GMP, which is an obligatory component in EDRF action, be measured and the endothelial requirement of any changes be assessed. It is also proposed that models suitable for the measurement of EDRF release be evaluated and utilized in an attempt to directly evaluate the hypothesis. In addition, it proposed that the time-course for development of tolerance be more clearly defined to determine the persistence of tolerance and also to study the time-course for the decay of tolerance after ethanol withdrawal. The final studies in this proposal are designed to evaluate the role of the endothelium in the action of ethanol in small diameter resistance vessels. These studies will utilize traditional pharmacologic techniques to evaluate ethanol induced changes in perfused vascular beds and will utilize closed-circuit video microscopy to evaluate ethanol induced changes in the diameter of microvessels. Both techniques will employ disulfiram to investigate the role of EDRF in the action of ethanol. Recent studies indicate that disulfiram may be a selective inhibitor of the release or action of EDRF. The long range goals of these studies is to obtain a clearer understanding of the effects of ethanol on the cardiovascular system and to understand the mechanisms utilized to produce tolerance to these effects.